Base station, terminal and communication method

ABSTRACT

A signal assignment unit ( 105 ) assigns a downlink control signal including resource assignment information of a PDSCH to a downlink resource. A specification unit ( 108 ) specifies a PUCCH resource using an offset value set to either a first PRB set or a second PRB set when the downlink control signal is disposed to spread over the first PRB set and the second PRB set. A signal separation unit ( 109 ) separates an ACK/NACK signal included in the specified PUCCH resource from a received signal from a terminal to which the downlink control signal has been transmitted.

TECHNICAL FIELD

The present disclosure relates to a base station, a terminal, and acommunication method.

BACKGROUND ART

In recent years, Machine-Type Communications (MTC), which uses acellular network, has been under study (see, e.g., Non-Patent Literature(hereinafter, referred to as “NPL”) 1). The applications of MTC possiblyinclude automatic meter reading of smart meters, and/or the inventorycontrol, logistics management and/or pet and domestic animal controlusing position information, and mobile payment and/or the like. In MTC,it is expected that a terminal that supports MTC (may be referred to asan MTC terminal or MTC UE) is connected to a network. Although a largenumber of MTC terminals are arranged, it is predicted that the amount oftraffic of each one of the MTC terminals is not so large. Therefore, theMTC terminals are desired to be low costs and low power consumption.Moreover, the MTC terminal is possibly placed in the underground or thelike of a building to which an electric wave is unlikely to reach, sothat coverage enhancement is also in demand.

In extension of LTE-Advanced, which has been standardized by 3GPP,limiting the resource used by an MTC terminal for communication to benot greater than 6 physical resource blocks (PRBs) regardless of asystem band has been under study for the purpose of achieving low-costsfor MTC terminals. When the system band is wider than 6 PRBs, the MTCterminal receives only part of the system band and performs transmissionand reception. The PRB used for transmission and reception is changeableby retuning. This resource not greater than 6 PRBs is called“Narrowband.” It is defined that this Narrowband is composed ofcontiguous PRBs.

Moreover, studies have been conducted on using MPDCCH (PDCCH for MTC)obtained by extending Enhanced Physical Downlink Control CHannel(EPDCCH), as a control signal for MTC terminals. MPDCCH is mapped in aPDSCH region in Narrowband. Moreover, in MTC, a method in which MPDCCHis assigned to all 6 PRB pairs included in Narrowband has been understudy for coverage enhancement. In EPDCCH, there are 16 EnhancedResource Element Groups (EREGs) per PRB pair, and when the number ofEREGs per Enhanced CCE (ECCE) is set to 4, the number of ECCEs of 6 PRBpairs becomes 24 ECCEs. In addition, ECCE is a unit for assigningEPDCCH, and EREG is a unit used for mapping ECCE to a Resource Element(RE). Moreover, a PRB pair is a resource unit and is composed of 1subframe (time domain)×12 subcarriers (frequency), and when a resourceon only the frequency domain is to be indicated, the resource may onlybe referred to as “PRB.”

For MPDCCH to be configured for MTC terminals, mapping of MPDCCHcomposed of 4 PRB pairs (4 PRB set) or MPDCCH composed of 2 PRB pairs (2PRB set) in 6 PRB pairs has been under study. Moreover, 1, 2, 4, 8, 16,and 24 have been discussed as the aggregation levels of MPDCCH. No that,each of the aggregation levels indicates the number of ECCEs formingMPDCCH. For aggregation levels=1, 2, 4, and 8, MPDCCH is mapped in 4 PRBset or 2 PRB set in a closed manner, and for aggregation level=16, oneMPDCCH is mapped to all 16 ECCEs in 4 PRB set.

Furthermore, for an MTC terminal with low channel quality, mapping ofone MPDCCH to all 6 PRB pairs in Narrowband, which overlap with anMPDCCH resource composed of 4 PRB pairs and 2 PRB pairs has been understudy. In this case, aggregation level=24, which may be simply referredto also as “24 ECCEs.”

CITATION LIST Non-Patent Literature

-   NPL 1-   3GPP TR 36.888 V12.0.0, and “Machine-Type Communications (MTC) User    Equipments (UEs) based on LTE (Release 12),” June 2013.

SUMMARY OF INVENTION Technical Problem

As with the traditional terminals, an MTC terminal receives MPDCCH,which is a downlink (DL) control signal, receives the downlink data(PDSCH) indicated by MPDCCH, and transmits an ACK/NACK signal of thereceived result via PUCCH, which is an uplink (UL) control signal. Inorder for each MTC terminal to identify a PUCCH resource for an MTCterminal in this case, use of an offset (called “N_pucch”) configuredfor each PRB set, as in the case of EPDCCH, has been discussed.

However, no studies have been conducted on how to define the offset(N_pucch) for “24 ECCEs” for mapping one MPDCCH to all 6 PRB pairs inNarrowband.

Thus, an aspect of the present disclosure provides a base station, aterminal, and a communication method each making it possible toefficiently identify a PUCCH resource of a case where one MPDCCH ismapped to all 6 PRB pairs in Narrowband.

Solution to Problem

A base station according to an aspect of the present disclosureincludes: a signal assignment section that assigns a downlink controlsignal to a downlink resource, the downlink control signal includingresource allocation information on Physical Downlink Shared Channel(PDSCH); an identifying section that identifies a Physical UplinkControl Channel (PUCCH) resource based on the downlink resource to whichthe downlink control signal has been assigned, the PUCCH resource beinga resource to which an ACK/NACK signal for the PDSCH is assigned; and asignal separating section that separates the ACK/NACK signal included inthe identified PUCCH resource from a received signal from a terminal towhich the downlink control signal has been transmitted, in which thedownlink resource is composed of a plurality of PRB pairs, and any of afirst PRB set and a second PRB set is assigned to each of the pluralityof PRB pairs, and in a case where the downlink control signal is mappedover the first PRB set and the second PRB set, the identifying sectionidentifies the PUCCH resource, using an offset value configured for anyof the first PRB set and the second PRB set.

A terminal according to an aspect of the present disclosure includes: areceiving section that receives a downlink control signal includingresource allocation information on Physical Downlink Shared Channel(PDSCH); and an identifying section that identifies a Physical UplinkControl Channel (PUCCH) resource based on a downlink resource to whichthe downlink control signal has been assigned, the PUCCH resource beinga resource to which an ACK/NACK signal for the PDSCH is assigned; and asignal assignment section that assigns the ACK/NACK signal to theidentified PUCCH resource, in which the downlink resource is composed ofa plurality of PRB pairs, and any of a first PRB set and a second PRBset is assigned to each of the plurality of PRB pairs, and in a casewhere the downlink control signal is mapped over the first PRB set andthe second PRB set, the identifying section identifies the PUCCHresource, using an offset value configured for any of the first PRB setand the second PRB set.

It should be noted that general or specific embodiments may beimplemented as a system, an apparatus, a method, an integrated circuit,a computer program or a storage medium, or any selective combination ofthe system, the apparatus, the method, the integrated circuit, thecomputer program, and the storage medium.

According to an aspect of the present disclosure, it is made possible toefficiently identify a PUCCH resource of a case where one MPDCCH ismapped to all 6 PRB pairs in Narrowband.

Additional benefits and advantages of the disclosed embodiments willbecome apparent from the specification and drawings. The benefits and/oradvantages may be individually obtained by the various embodiments andfeatures of the specification and drawings, which need not all beprovided in order to obtain one or more of such benefits and/oradvantages.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a conceptual diagram of a PUCCH resource;

FIG. 2A is a diagram illustrating an example of an MPDCCH mapping method(Option 1);

FIG. 2B is another diagram illustrating another example of the MPDCCHmapping method (Option 1);

FIG. 3A is a diagram illustrating an example of an MPDCCH mapping method(Option 2);

FIG. 3B is another diagram illustrating the example of the MPDCCHmapping method (Option 2)

FIG. 4 is a block diagram illustrating a main configuration of a basestation;

FIG. 5 is a block diagram illustrating a main configuration of aterminal;

FIG. 6 is a block diagram illustrating a configuration of the basestation;

FIG. 7 is a block diagram illustrating a configuration of the terminal;

FIG. 8 is a diagram illustrating an example of a PUCCH resourceidentification method according to Operation Example 1 of Embodiment 1;

FIG. 9 is a conceptual diagram of a PUCCH resource;

FIG. 10 is a diagram provided for describing a problem of Embodiment 3;

FIG. 11 is another diagram provided for describing the problem ofEmbodiment 3;

FIG. 12A is a diagram illustrating an example of an MPDCCH mappingmethod according to Operation Example 6 of Embodiment 3;

FIG. 12B is a diagram illustrating an example of an MPDCCH mappingmethod according to Operation Example 6 of Embodiment 3;

FIG. 12C is a diagram illustrating an example of an MPDCCH mappingmethod according to Operation Example 6 of Embodiment 3;

FIG. 13A is a diagram illustrating a 4 PRB set assignment exampleaccording to a variation; and

FIG. 13B is a diagram illustrating a 2 PRB set assignment exampleaccording to a variation.

DESCRIPTION OF EMBODIMENTS Knowledge as Foundation of Present Disclosure

Use of an offset (N_pucch) for identifying a PUCCH resource directed toan MTC terminal makes it possible to distinguish between a traditionalterminal PUCCH resource and an MTC terminal PUCCH resource and thus toavoid a collision of PUCCH resources. Moreover, N_pucch can avoid acollision of PUCCH resources between MTC terminals of differentrepetition levels when an indication is given for each repetition level.Thus, a distance problem that occurs when signals of terminals havingmutually different distances to a base station are multiplexed can besolved.

In N_pucch for a single MTC, a collision of PUCCH resources between aplurality of MTC terminals of the same repetition level cannot beavoided, however.

In this respect, for PUCCH resources of MTC terminals of the samerepetition level, it may be possible to identify a resource of PUCCHformat 1a/1b for transmitting an ACK/NACK based on mapping of a DLcontrol signal (MPDCCH) by which DL assignment indicating transmissionof a DL data signal as in the case of EPDCCH.

In EPDCCH, offset N_(PUCCH, q) ^((e1)) (hereinafter, referred to as“N_pucch, q” for simplicity) is configured for each EPDCCH-PRB-set q=0,1, and a PUCCH resource is identified from an ECCE number. In EPDCCH, aresource (resource number) of PUCCH format 1a/1b is identified by thefollowing expressions.

$\begin{matrix}{\mspace{79mu}{{{distributed}\mspace{14mu}{assignment}\text{:}}\mspace{20mu}{n_{PUCCH}^{({1,{\overset{\sim}{p}}_{0}})} = {n_{{ECCE},q} + \Delta_{ARO} + N_{{PUCCH},q}^{(\;{e\; 1})}}}\mspace{20mu}{{localized}\mspace{14mu}{assignment}\text{:}}{n_{PUCCH}^{({1,{\overset{\sim}{p}}_{0}})} = {{\left\lfloor \frac{n_{{ECCE},q}}{N_{RB}^{{ECCE},q}} \right\rfloor \cdot N_{RB}^{{ECCE},q}} + n^{\prime} + \Delta_{ARO} + N_{{PUCCH},q}^{(\;{e\; 1})}}}}} & \left\lbrack {{Expression}\mspace{14mu} 1} \right\rbrack\end{matrix}$

In Expression 1, n_(ECCE, q) represents an offset by the original ECCEnumber to which a DCI (Downlink Control Information) is mapped in theq-th EPDCCH PRB set. Moreover, Δ_(ARO) represents an offset indicated by2-bit ARO (ACK/NACK Resource Offset) included in the DCI, and the offsettakes values of −2, −1, 0, and +2 in case of FDD. Moreover, N_(PUCCH, q)^((e1)) is indicated for each terminal by a higher layer. Moreover,N_(RB) ^(ECCE,q) represents the number of ECCEs per RB, and n′represents an offset based on an antenna port.

FIG. 1 is a conceptual diagram of the PUCCH resource mentioned above.

As illustrated in FIG. 1 , by configuring offset values N_(PUCCH,0)^((e1)) and N_(PUCCH,1) ^((e1)) to have values distant from each other,the PUCCH resources corresponding to the respective PRB sets are mappedso as not to overlap with each other, so that a collision of PUCCHresources can be avoided. Moreover, by configuring N_(PUCCH, 0) ^((e1))and N_(PUCCH, 1) ^((e1)) to have values close to each other, the PUCCHresources corresponding to the respective PRB sets are mapped so as tooverlap with each other, so that the entirety of PUCCH resources canalso be reduced.

It is conceivable to identify a PUCCH resource for MPDCCH as in the caseof EPDCCH. In this case, for the MPDCCH to be mapped in a PRB setcomposed of 4 PRB pairs or 2 PRB pairs, a PUCCH resource can beidentified by a method similar to the method for EPDCCH mentioned above.

There is, however, a problem in that the same method as that for EPDCCHcannot be applied for a PUCCH resource of a case where MPDCCH is mappedto 24 ECCEs in Narrowband (i.e., a case where MPDCCH is mapped over 4PRB set and 2 PRB set), and it is thus impossible to identify aresource. Note that, although it is conceivable to separately indicatean offset corresponding to MPDCCH of 24 ECCEs, the amount of signalingincreases in this case.

Hereinafter, a description will be given of a method for identifying aPUCCH resource without any increase in the amount of signaling in a casewhere MPDCCH is mapped to 24 ECCEs in a narrowband.

Hereinafter, a detailed description will be given of an embodiment ofthe present disclosure with reference to the accompanying drawings.

[Description of MTC 24 ECCEs]

As mentioned above, MPDCCH of 24 ECCEs used in MTC is mapped to all REswhich are included in 6 PRB pairs in Narrowband and which are availablefor MPDCCH. Hereinafter, a description will be given of two Options 1and 2 each conceivable as a mapping method for MPDCCH of 24 ECCEs.

(Option 1: FIGS. 2A and 2B)

In Option 1, MPDCCH of 24 ECCEs is mapped to a frequency first(Frequency first). More specifically, in Narrowband, a symbol sequenceof MPDCCH is mapped from an OFDM symbol with a low OFDM symbol number inascending order of frequency while vertically crossing over PRB pairs,and then moves to the next OFDM symbol and is mapped in ascending orderof frequency while vertically crossing over PRB pairs, likewise.

FIGS. 2A and 2B illustrate an MPDCCH mapping example of Option 1.

In FIG. 2A, 2 PRB set is assigned to PRB pairs #0 and #1, and 4 PRB setis assigned to PRB pairs #2 to #5. In FIG. 2A, MPDCCH of 24 ECCEs ismapped to all REs available for MPDCCH without distinction between 2 PRBset resources (PRB pairs #0, #1) and 4 PRB set resources (PRB pairs #2to #5).

In FIG. 2B, 2 PRB set is assigned to PRB pairs #2 and #3, and 4 PRB setis assigned to PRB pairs #0, #1, #4, and #5. In FIG. 2B, as in FIG. 2A,MPDCCH of 24 ECCEs is mapped to all REs available for MPDCCH withoutdistinction between 2 PRB set resources (PRB pairs #2, #3) and 4 PRB setresources (PRB pairs #0, #1, #4, #5).

(Option 2: FIGS. 3A and 3B)

In Option 2, MPDCCH of 24 ECCEs is mapped to an MPDCCH PRB set first inNarrowband. Accordingly, the mapping order of MPDCCH is changeddepending on which PRB pair the PRB set is assigned to.

FIGS. 3A and 3B illustrate an MPDCCH mapping example of Option 2 inwhich MPDCCH is mapped to 4 PRB set, first. More specifically, MPDCCH isfirst mapped to REs in the 4 PRB set and then mapped to REs in 2 PRBset. Note that, mapping in 4 PRB set and 2 PRB set is performedFrequency first as in EPDCCH. More specifically, in PRB pairs in a PRBset, the symbol sequence of MPDCCH is mapped from an OFDM symbol with alow OFDM symbol number in ascending order of frequency while verticallycrossing over PRB pairs, and then moves to the next OFDM symbol and ismapped in ascending order of frequency while vertically crossing overPRB pairs, likewise.

In FIG. 3A, 2 PRB set is assigned to PRB pairs #0 and #1, and 4 PRB setis assigned to PRB pairs #2 to #5. Accordingly, in FIG. 3A, MPDCCH of 24ECCEs is mapped to PRB pairs #2 to #5 to which 4 PRB set is assigned,and then mapped to PRB pairs #0 and #1 to which 2 PRB set is assigned.

In FIG. 3B, 2 PRB set is assigned to PRB pairs #2 and #3, and 4 PRB setis assigned to PRB pairs #0, #1, #4, and #5. Accordingly, in FIG. 3B,MPDCCH of 24 ECCEs is mapped to PRB pairs #0, #1, #4, and #5 to which 4PRB set is assigned, and then mapped to PRB pairs #2 and #3 to which 2PRB set is assigned.

Note that, hereinafter, in any of Options, the minimum ECCE number of acase where MPDCCH of 24 ECCE is detected is assumed to be n_(ECCE,q)=0.

[Overview of Communication System]

A communication system according to each embodiment of the presentdisclosure includes base station 100 and terminal 200 each supportingthe LTE-Advanced system, for example. Terminal 200 is an MTC terminal,for example.

FIG. 4 is a block diagram illustrating a main configuration of basestation 100 according to the embodiment of the present disclosure. Inbase station 100 illustrated in FIG. 4 , signal assignment section 105assigns a downlink control signal (MPDCCH) including PDSCH resourceassignment information to a downlink resource (Narrowband). PUCCHresource identifying section 108 identifies the PUCCH resource to whichan ACK/NACK for PDSCH is to be assigned, based on the downlink resourceto which the downlink control signal has been assigned. Signalseparating section 109 separates the ACK/NACK signal included in theidentified PUCCH resource from a received signal from the terminal towhich the downlink control signal has been transmitted.

Moreover, FIG. 5 is a block diagram illustrating a main configuration ofterminal 200 according to each embodiment of the present disclosure. Interminal 200 illustrated in FIG. 5 , MPDCCH receiving section 207receives a downlink control signal (MPDCCH) including PDSCH resourceassignment information. PUCCH resource identifying section 208identifies the PUCCH resource to which an ACK/NACK signal for PDSCH isto be assigned, based on the downlink resource to which the downlinkcontrol signal has been assigned. Signal assignment section 211 assignsan ACK/NACK signal to the identified PUCCH resource.

In addition, the above-mentioned downlink resource (Narrowband) iscomposed of a plurality of PRB pairs, and any of the 1st PRB set and the2nd PRB set is assigned to each of the plurality of PRB pairs. PUCCHresource identifying section 108 (208) identifies the PUCCH resourceusing the offset value configured for any of the 1st PRB set and the 2ndPRB set in a case where a down control signal is mapped over the 1st PRBset and the 2nd PRB set described above.

Embodiment 1

[Configuration of Base Station]

FIG. 6 is a block diagram illustrating a configuration of base station100 according to the present embodiment. In FIG. 6 , base station 100includes aggregation level configuration section 101, MPDCCH generationsection 102, error correction coding section 103, modulation section104, signal assignment section 105, transmitting section 106, receivingsection 107, PUCCH resource identifying section 108, signal separatingsection 109, PUCCH receiving section 110, demodulation section 111, anderror correction decoding section 112.

Aggregation level configuration section 101 configures an aggregationlevel for an MTC terminal based on receiving quality of the MTC terminaland the number of information bits of MPDCCH (not illustrated) which areheld by base station 100. Aggregation level configuration section 101outputs the configured aggregation level to MPDCCH generation section102.

MPDCCH generation section 102 generates MPDCCH which is the controlinformation directed to the MTC terminal. More specifically, MPDCCHgeneration section 102 generates the information bit of MPDCCH, applieserror correction coding thereto, generates a transmission bit sequenceby rate matching from the aggregation level inputted from aggregationlevel configuration section 101, and the number of REs available forMPDCCH, and outputs the transmission bit sequence to signal assignmentsection 105. MPDCCH includes DL assignment information indicating PDSCHresource allocation, and UL assignment information indicating PUSCHresource allocation, for example. Moreover, the DL assignmentinformation is outputted to signal assignment section 105, and the ULassignment information is outputted to signal separating section 109.

Error correction coding section 103 applies error correction coding to atransmission data signal (DL data signal) or higher layer signaling andoutputs the encoded signal to modulation section 104.

Modulation section 104 applies modulation processing to the signalreceived from error correction coding section 103 and outputs themodulated data signal to signal assignment section 105.

Signal assignment section 105 assigns the signal (including data signal)received from modulation section 104, and the control signal (MPDCCH)received from MPDCCH generation section 102 to a predetermined downlinkresource. For example, when the aggregation level of MPDCCH is 1, 2, 4,or 8, signal assignment section 105 assigns MPDCCH to either PRB set 0or PRB set 1 in Narrowband, and when the aggregation level of MPDCCH is16, signal assignment section 105 assigns MPDCCH to a PRB set having thenumber of PRBs equal to 4. Furthermore, when the aggregation level is 24(24 ECCEs), signal assignment section 105 assigns MPDCCH to all ECCEs inNarrowband over PRB set 0 and PRB set 1 in Narrowband. Moreover, signalassignment section 105 assigns a signal directed to an MTC terminal toNarrowband among a transmission data signal and higher layer signaling.In this manner, a transmission signal is formed by assigning a controlsignal (MPDCCH) and a data signal (PDSCH) to a predetermined resource.The transmission signal thus formed is outputted to transmitting section106. Moreover, signal assignment section 105 outputs assignmentinformation (e.g., the PRB set number, the minimum ECCE number, and AROincluded in the DL assignment information to which MPDCCH has beenmapped) indicating the resource to which MPDCCH is assigned, to PUCCHresource identifying section 108.

Transmitting section 106 applies radio transmission processing, such asup-conversion, to the transmission signal inputted from signalassignment section 105, and transmits the processed signal to terminal200 via an antenna.

Receiving section 107 receives, via an antenna, the signal transmittedfrom terminal 200, and applies radio reception processing, such asdown-conversion, to the received signal, and outputs the processedsignal to signal separating section 109.

PUCCH resource identifying section 108 identifies a PUCCH resource towhich an ACK/NACK signal for the data signal (PDSCH) indicated by theMPDCCH is assigned, based on the downlink resource which is indicated bythe assignment information inputted from signal assignment section 105and to which the MPDCCH is assigned. PUCCH resource identifying section108 outputs the information indicating the identified PUCCH resource tosignal separating section 109. In addition, the PUCCH resourceidentifying method in PUCCH resource identifying section 108 will bedescribed in detail, hereinafter.

Signal separating section 109 separates a UL data signal from thereceived signal based on the information inputted from MPDCCH generationsection 102 and outputs the separated signal to demodulation section111. Moreover, signal separating section 109 separates the signal(including ACK/NACK signal) included in the PUCCH resource from thereceived signal based on the information inputted from PUCCH resourceidentifying section 108 and outputs the signal to PUCCH receivingsection 110.

PUCCH receiving section 110 determines an ACK and NACK from the signal(PUCCH) inputted from signal separating section 109 and indicates thedetermination result to a higher layer.

Demodulation section 111 applies demodulation processing to the signalinputted from signal separating section 109 and outputs the signalacquired by the demodulation processing to error correction decodingsection 112.

Error correction decoding section 112 decodes the signal inputted fromdemodulation section 111 and acquires a received data signal fromterminal 200.

[Configuration of Terminal]

FIG. 7 is a block diagram illustrating a configuration of terminal 200according to the present embodiment. In FIG. 7 , terminal 200 includesreceiving section 201, signal separating section 202, demodulationsection 203, error correction decoding section 204, error determinationsection 205, ACK/NACK generation section 206, MPDCCH receiving section207, PUCCH resource identifying section 208, error correction codingsection 209, modulation section 210, signal assignment section 211, andtransmitting section 212.

Receiving section 201 identifies to which Narrowband within a systemband the signal has been assigned, based on a predetermined pattern, orinformation (not illustrated) indicated by a higher layer, and appliesretuning to the identified Narrowband. Receiving section 201 thenreceives a received signal via an antenna, applies reception processing,such as down-conversion, to the received signal, and then outputs theprocessed signal to signal separating section 202.

Signal separating section 202 outputs, to MPDCCH receiving section 207,the signal (MPDCCH signal) mapped to a PRB to which MPDCCH may have beenassigned. Moreover, signal separating section 202 separates a DL datasignal and higher layer signaling from the received signal based on theDL assignment information inputted from MPDCCH receiving section 207,and outputs the DL data signal and higher layer signaling todemodulation section 203.

Demodulation section 203 demodulates the signal received from signalseparating section 202 and outputs the demodulated signal to errorcorrection decoding section 204.

Error correction decoding section 204 decodes the demodulated signalreceived from demodulation section 203 and outputs the received datasignal acquired by decoding. Moreover, the received data signal isoutputted to error determination section 205.

Error determination section 205 detects an error by CRC of the receiveddata signal and outputs the detection result to ACK/NACK generationsection 206.

ACK/NACK generation section 206 generates an ACK when there is no error,and generates a NACK when there is an error, based on the detectionresult of the received data signal inputted from error determinationsection 205, and outputs the generated ACK/NACK signal to a higher layerand signal assignment section 211.

MPDCCH receiving section 207 detects MPDCCH which is a control signalincluding DL assignment information or UL assignment information byattempting reception of the MPDCCH signal received from signalseparating section 202 with respect to search space for each PRB set 0and PRB set 1, and “24 ECCEs” assigned to all ECCEs in Narrowband overPRB set 0 and PRB set 1. MPDCCH receiving section 207 outputs the DLassignment information detected as a signal directed to terminal 200 ofMPDCCH receiving section 207, to signal separating section 202, andoutputs the UL assignment information to signal assignment section 211.Moreover, MPDCCH receiving section 207 outputs the assignmentinformation indicating the PRB set number, the minimum ECCE number, andARO included in DL the assignment information, to which the MPDCCH hasbeen mapped, to PUCCH resource identifying section 208.

PUCCH resource identifying section 208 identifies the PUCCH resource towhich an ACK/NACK for the received data signal is assigned, based on theassignment information inputted from MPDCCH receiving section 207 (PRBset number, the minimum ECCE number, and ARO), and the N_pucchinformation that is previously indicated by a higher layer. PUCCHresource identifying section 208 outputs the information indicating theidentified PUCCH resource to signal assignment section 211. No that, thePUCCH resource identifying method in PUCCH resource identifying section208 will be described in detail, hereinafter.

Error correction coding section 209 applies error correction coding tothe transmission data signal (UL data signal) and outputs the encodeddata signal to modulation section 210.

Modulation section 210 modulates the data signal received from errorcorrection coding section 209 and outputs the modulated data signal tosignal assignment section 211.

Signal assignment section 211 assigns the data signal inputted frommodulation section 210 to a resource based on the UL assignmentinformation received from MPDCCH receiving section 207 and outputs theresultant to transmitting section 212. Moreover, signal assignmentsection 211 assigns the ACK/NACK signal inputted from ACK/NACKgenerating section 206 to a PUCCH resource based on the PUCCH resourceallocation information inputted from PUCCH resource identifying section208, and outputs the resultant to transmitting section 212.

Transmitting section 212 identifies the resource corresponding toNarrowband to which UL data is assigned, based on the predeterminedpattern and applies retuning. Transmitting section 212 appliestransmission processing, such as up-conversion, to the signal inputtedfrom signal assignment section 211, and transmits the processed signalvia an antenna.

[Operations of Base Station 100 and Terminal 200]

The operations of base station 100 and terminal 200 each configured inthe manner described above will be described in detail.

In the present embodiment, in a case where MPDCCH is mapped over aplurality of PRB sets (4 PRB set and 2 PRB set) (i.e., case of MPDCCH of24 CCEs), base station 100 (PUCCH resource identifying section 108) andterminal 200 (PUCCH resource identifying section 208) identify a PUCCHresource, using an offset value (N_pucch) configured for any of theplurality of PRB sets.

Hereinafter, Operation Examples 1 and 2 according to the presentembodiment will be described.

Operation Example 1

In Operation Example 1, when detecting MPDCCH of 24 ECCEs, terminal 200(MTC terminal) identifies a PUCCH resource, using an offset value (MTCN_pucch) configured for a PRB set assigned to a PRB pair having aminimum PRB number among the PRB sets in Narrowband in both Options 1and 2.

For example, in FIG. 2A of Option 1, and FIG. 3A of Option 2, terminal200 identifies a PUCCH resource, using N_pucch corresponding to the 2PRB set assigned to PRB pair #0. Meanwhile, in FIG. 2B of Option 1, andFIG. 3B of Option 2, terminal 200 identifies a PUCCH resource, usingN_pucch corresponding to 4 PRB set assigned to PRB #0.

Moreover, base station 100 identifies, as in the case of terminal 200, aPUCCH resource to which an ACK/NACK signal is assigned, using an offsetvalue (MTC N_pucch) configured for a PRB set assigned to a PRB pairhaving a minimum PRB number among the PRB sets in Narrowband to whichMPDCCH is assigned.

In a case where the PUCCH resource corresponding to MPDCCH of 24 ECCEsis identified in the manner described above, the offset value N_pucch tobe configured for MPDCCH of 24 ECCEs differs in accordance withassignment of a PRB set of MPDCCH to a PRB pair, as described above.Accordingly, the PUCCH resource corresponding to MPDCCH of 24 ECCEs canbe switched by assignment of a PRB set of MPDCCH.

FIG. 8 illustrates a PUCCH resource allocation example of a case wheretwo Narrowbands 1 and 3 are used for different MTC terminals (terminals200), and MPDCCH of 24 ECCEs is detected in both Narrowbands.

In FIG. 8 , N_pucch, 0 is configured for 2 PRB set, and N_pucch, 1 isconfigured for 4PRB set. Moreover, assignment of PRB set differs betweentwo Narrowbands illustrated in FIG. 8 . More specifically, in Narrowband1, as in FIG. 2A, 2 PRB set is assigned to PRB pairs #0 and #1, and 4PRB set is assigned to PRB pairs #2 to #5. Meanwhile, in Narrowband 3,as in FIG. 2B, 2 PRB set is assigned to PRB pairs #14 and #15, and 4PRBset is assigned to PRB pairs #12, #13, #16, and #17.

In this case, the MTC terminal that uses Narrowband 1 identifies a PUCCHresource, using N_pucch, 0 configured for 2 PRB set assigned to PRB pair#0 having the minimum PRB number. Meanwhile, the MTC terminal that usesNarrowband 3 identifies a PUCCH resource, using N_pucch, 1 configuredfor 4 PRB set assigned to PRB pair #12 having the minimum PRB number.

Accordingly, as illustrated in FIG. 8 , even when MPDCCH of 24 ECCEs hasbeen simultaneously mapped in two Narrowbands 1 and 3, each of the MTCterminals identifies a PUCCH resource, using different N_pucch, so thata collision of PUCCH resources can be prevented.

Operation Example 2

In Operation Example 2, when detecting MPDCCH of 24 ECCEs in bothOptions 1 and 2, terminal 200 (MTC terminal) identifies a PUCCHresource, using an offset value (N_pucch, 0) configured for a PRB sethaving the minimum PRB set number among the PRB sets in Narrowband.

N_pucch, 0 is N_pucch configured for PRB set 0 (first PRB set), herein.Which PRB set is PRB set 0 or PRB set 1 among 2 PRB set and 4 PRB setmay be indicated during configuration performed in a higher layer (RRCsignaling), or one of the PRB sets may be previously defined to be PRBset 0. Moreover, N_pucch, 0 and N_pucch, 1 are indicated to terminal 200by the higher layer (RRC signaling). The higher layer signaling may bean SIB for MTC which can be received in common by MTC terminals orsignaling specific to terminal 200.

Moreover, as in the case of terminal 200, base station 100 identifies aPUCCH resource to which an ACK/NACK signal is assigned, using an offsetvalue (N_pucch, 0) configured for a PRB set having the minimum PRB setnumber among PRB sets in Narrowband to which MPDCCH is assigned.

Thus, when the PUCCH resource corresponding to MPDCCH of 24 ECCEs is tobe identified in the manner described above, N_pucch, 0 is always usedindependently of which PRB pair each PRB set is assigned to inNarrowband.

Moreover, when 24 ECCEs are used without assumption of MU-MIMO, anotherMPDCCH is not mapped in Narrowband in which 24 ECCEs are mapped.Therefore, in order to avoid generating an unnecessary blank resource,it is desirable to use a PUCCH resource having a low resource number. Inthis respect, using N_pucch, 0 in a case where a PUCCH resourcecorresponding to MPDCCH of 24 ECCEs is to be identified, it can beexpected that a PUCCH resource having a low resource number isconfigured. Thus, reduction of PUCCH resources can be achieved, and aPUSCH resource can be secured more widely. Note that, it is assumedherein that the value of N_pucch, 0 is smaller than the value ofN_pucch, 1.

Moreover, when MPDCCH is transmitted in another Narrowband and the sameN_pucch, 0 and n_(ECCE, 0)=0 are used under assumption of MU-MIMO, acollision of PUCCH resources occurs. However, the collision of PUCCHresources can be avoided by ARO in this case.

Variation of Operation Example 2

Note that, in Operation Example 2, it is possible to set a rule that,when an MTC terminal detects MPDCCH of 24 ECCEs, a PUCCH resource isidentified using N_pucch, 1. In this case, configuring N_pucch, 1 tohave a value smaller than N_pucch, 0 makes it possible to achievereduction of PUCCH resources.

Moreover, it is possible to set a rule that, when an MTC terminaldetects MPDCCH of 24 ECCEs, a PUCCH resource is identified using one ofN_pucch, 0 and N_pucch, 1 whichever has a smaller value than the other.In this case, reduction of PUCCH resources can be achieved irrespectiveof the magnitude relationship of N_pucch, 0 and N_pucch, 1.

Moreover, it is possible to set a rule that, when an MTC terminaldetects MPDCCH of 24 ECCEs, a PUCCH resource is identified using N_pucchcorresponding to 4 PRB set or N_pucch corresponding to 2 PRB set. Inthis case, configuring N_pucch corresponding to 4 PRB set or N_pucchcorresponding to 2 PRB set to have a small value makes it possible toachieve reduction of PUCCH resources.

Operation Examples 1 and 2 according to the present embodiment have beendescribed thus far.

As described above, in the present embodiment, in a case where MPDCCH ismapped over a plurality of PRB sets, base station 100 and terminal 200identify a PUCCH resource, using N_pucch, q corresponding to any of theplurality of PRB sets q to which the MPDCCH is mapped.

In the manner described above, base station 100 and terminal 200 canidentify the PUCCH resource corresponding to MPDCCH mapped over aplurality of PRB sets, as with 24 ECCEs, without addition of newsignaling. That is, according to the present embodiment, the PUCCHresource of the case where one MPDCCH is mapped to all 6 PRB pairs inNarrowband can be efficiently identified.

In addition, in MPDCCH mapping of Option 2, in the operation exampledescribed above, a description has been given with an example of a casewhere an assumption is made that, PRB set 0 (first PRB set) indicated bya higher layer is 4 PRB set while PRB set 1 (second PRB set) is 2 PRBset, and MPDCCH is mapped to 4 PRB set first. It is, however, MPDCCH maybe mapped to PRB set 1 (second PRB set) first.

Embodiment 2

A base station and a terminal according to Embodiment 2 have basicconfigurations common to base station 100 and terminal 200 according toEmbodiment 1, so that a description will be given while FIGS. 6 and 7are incorporated herein.

In Embodiment 1, a description has been given of the case where anassumption is made that different offset values N_pucch are configuredfor a plurality of PRB sets. Meanwhile, in this embodiment, adescription will be given of a case where an assumption is made that acommon offset value N_pucch is configured for a plurality of PRB sets.

The PUCCH resource corresponding to MPDCCH in this embodiment will bedescribed, hereinafter.

For PUCCH of MTC terminals of the same repetition level, commonN_(PUCCH) ^((e1)) (hereinafter, simply referred to as “N_pucch”) isconfigured for PRB sets, and a PUCCH resource is identified from an ECCEnumber for each PRB set. The PUCCH resource (resource number) fortransmitting PUCCH format 1a/1b is identified by the followingexpressions.

$\begin{matrix}{\mspace{79mu}{{{distributed}\mspace{14mu}{assignment}\text{:}}\mspace{20mu}{n_{PUCCH}^{({1,{\overset{\sim}{p}}_{0}})} = {n_{{ECCE},q} + \Delta_{ARO} + N_{{PUCCH},q}^{(\;{e\; 1})} + K_{q}}}\mspace{20mu}{{localized}\mspace{14mu}{assignment}\text{:}}{n_{PUCCH}^{({1,{\overset{\sim}{p}}_{0}})} = {{\left\lfloor \frac{n_{{ECCE},q}}{N_{RB}^{{ECCE},q}} \right\rfloor \cdot N_{RB}^{{ECCE},q}} + n^{\prime} + \Delta_{ARO} + N_{{PUCCH},q}^{(\;{e\; 1})} + K_{q}}}}} & \left\lbrack {{Expression}\mspace{14mu} 2} \right\rbrack\end{matrix}$

In the case of PRB set 0 (q=0), K₀=0, and in the case of PRB set 1(q=1), K₁ represents the number of ECCEs included in PRB set 0. Forexample, when PRB set 0 is 4 PRB set (16 ECCEs), K₁=16, and when PRB set1 is 2 PRB set (8 ECCEs), K₁=8.

FIG. 9 illustrates a conceptual diagram of a PUCCH resource of thepresent embodiment.

As illustrated in FIG. 9 , the PUCCH resource (PUCCH set (0))corresponding to PRB set 0 is identified using N_pucch and an ECCEnumber, and the PUCCH resource (PUCCH set (1)) corresponding to PRB set1 is identified using N_pucch+ECCE number+K₁ (provided that, K₁ is thenumber of ECCEs in PUCCH set (0)). Thus, the PUCCH resourcecorresponding to PRB set 0 and the PUCCH resource corresponding to PRBset 1 are configured to be contiguous resources. Therefore, when allMPDCCHs are transmitted using aggregation level 1, the PUCCH resourcefor PRB set 1 can be mapped after the PUCCH resource corresponding toPRB set 0 is secured, without using ARO.

In the present embodiment, base station 100 and terminal 200 identify aPUCCH resource corresponding to MPDCCH (MPDCCH of 24 ECCEs) mapped overa plurality of PRB sets, using common N_pucch.

Hereinafter, Operation Example 3 according to the present embodimentwill be described.

Operation Example 3

In Operation Example 3, when detecting MPDCCH of 24 ECCEs, base station100 and terminal 200 (MTC terminal) identify a PUCCH resource, usingN_pucch configured in common to a plurality of PRB sets in Narrowband inboth Options 1 and 2. At this time, Kq=0 irrespective of which PRB pairs4 PRB set and 2 PRB set are assigned to. Moreover, in a case where anassumption is made that the minimum ECCE number of a case of usingMPDCCH of 24 ECCEs is n_(ECCE,q)=0, a PUCCH resource (resource number)is identified by the following expressions.distributed assignment: n _(PUCCH) ^((1,{tilde over (p)}) ⁰ ⁾=Δ_(ARO) +N_(PUCCH) ^((e1))localized assignment: n _(PUCCH) ^((1,{tilde over (p)}) ⁰ ⁾ =n′Δ _(ARO)+N _(PUCCH) ^((e1))  [Expression 3]

As described above, when base station 100 and terminal 200 identify thePUCCH resource corresponding to MPDCCH of 24 ECCEs based on commonN_pucch, a PUCCH resource having a low resource number can be alwaysconfigured as the PUCCH resource corresponding to MPDCCH of 24 ECCEsirrespective of assignment of an MPDCCH PRB set to a PRB pair.

Thus, it is made possible to avoid a situation where an unnecessaryblank PUCCH resource is secured and to achieve reduction of PUCCHresources, and as a result of this, the PUSCH resource can be securedmore widely.

Moreover, according to the present embodiment, base station 100 andterminal 200 can identify the PUCCH resource corresponding to MPDCCHmapped over a plurality of PRB sets as with 24 ECCEs without addition ofnew signaling as in Embodiment 1. That is, according to the presentembodiment, the PUCCH resource of the case where one MPDCCH is mapped toall 6 PRB pairs in Narrowband can be efficiently identified.

Note that, in a case where MPDCCH is transmitted and the same N_pucch, 0and n_(ECCE, 0)=0 are used in another Narrowband under assumption ofMU-MIMO, as in Operation Example 2 of the Embodiment 1, a collision ofPUCCH resources occurs. In this case, however, the collision of PUCCHresources can be avoided by ARO.

Moreover, although the case where the PUCCH resource corresponding to aPRB set is changed for each PRB set q using variable K_(q) has beendescribed in the present embodiment, the PUCCH resource may be sharedbetween PRB sets q without using K_(q). In this case, the collision ofPUCCH resources between PRB sets q may be avoided by ARO. In particular,it is predicted that PUCCH resources are not crowded in a case whereMPDCCH with a high aggregation level is used as in MPDCCH of 24 ECCEs,so that the collision can be avoided by only ARQ. As described above, bysharing PUCCH resource between PRB sets q, the amount of PUCCH resourcecan be reduced. Moreover, in this case as well, the PUCCH resource of acase where MPDCCH of 24 ECCEs is detected can be found by an expressionsimilar to that of Operation Example 3.

Moreover, although a description has been given with the case where K₁is set to be the number of ECCEs included in PRB set 0 in the presentembodiment, the value of K₁ is not limited to this and may be a valueindicating ½ of the number of ECCEs included in PRB set 0, for example.When K₁ is set to a small value such as ½ of the number of ECCEs, theentirety of the amount of PUCCH resources can be reduced. This iseffective, for example, when the probability of a collision of PUCCHresources is low.

Embodiment 3

When MPDCCH of 24 ECCEs is mapped to an MPDCCH PRB set first inNarrowband as described in Option 2, there may be a case where an MTCterminal erroneously recognizes reception as having received a maximumaggregation signal of an MPDCCH PRB set to which MPDCCH has been mappedfirst (hereinafter, referred to as “erroneous recognition 1”) and a casewhere an MTC terminal erroneously recognizes reception as havingreceived a maximum aggregation level signal of an MPDCCH PRB set towhich MPDCCH has been mapped second (hereinafter, referred to as“erroneous recognition 2”).

Hereinafter, for simplicity of description, an assumption is made that24 ECCEs are mapped to PRB set 0, first. Hereinafter, the erroneousrecognition described above and possible problems associated therewithwill be described using FIGS. 10 and 11 .

Erroneous recognition 1 may occur when the number of transmittable bitswhich is calculated from the number of REs available for MPDCCH in PRBset 0 becomes an integral multiple of the number of after encoding bitsof MPDCCH. Moreover, erroneous recognition 2 may occur, in addition tothe above condition of erroneous recognition 1, when the number oftransmittable bits which is calculated from the number of REs availablefor MPDCCH in PRB set 1 becomes an integral multiple of the number ofafter encoding bits of MPDCCH.

FIG. 10 illustrates a case where the number of after encoding bits ofMPDCCH is equal to the number of transmittable bits in aggregation level8 (8 ECCEs). Accordingly, the transmission bit sequence of 24 ECCEs isgenerated, by rate matching, as a bit sequence which is three times thebit sequence by copying the after encoding bits. As illustrated in FIG.10 , the generated transmission bit sequence is mapped to 16 ECCEs of 4PRB set, which is PRB set 0, and then, is mapped to 8 ECCEs of 2 PRBset, which is PRB set 1.

When the number of after encoding bits of MPDCCH is equal to the numberof transmittable bits in another aggregation level, it is not necessaryto reduce the bits at the time of rate matching. For this reason, thetransmission bit sequence of the first-half 16 ECCEs and the second-half8 ECCEs of the transmission bit sequence of 24 ECCEs illustrated in FIG.10 becomes a bit sequence receivable as 16 ECCEs or 8 ECCEs (i.e., bitsequence is one that is erroneously recognized as 16 ECCEs or 8 ECCEs)in an MTC terminal when the reception quality in the MTC terminal ishigh.

Note that, whether bits are reduced or not at the time of rate matchingdiffers depending on the number of REs available for MPDCCHtransmission. Moreover, the number of REs available for MPDCCHtransmission is variable depending on the PDCCH length, the number ofCRS ports, the number of CSI-RS ports, and/or CP length, for example.Therefore, it is difficult to cover all patterns as to under whatconditions the problems of erroneous recognition occur for MPDCCH.Meanwhile, in PDCCH, when a similar problem occurs, the measure to add apadding bit to information bits is taken. This is because the number ofREs used for transmission of each aggregation level is fixed. Moreover,in EPDCCH, this problem is avoided by mapping of EPDCCH to REs isconfigured to be Frequency first.

Moreover, the erroneous recognition occurs when the actual receptionquality of an MTC terminal is greater than the reception quality of theMTC terminal which has been predicted by the base station, and MPDCCHcan be received in the MTC terminal with aggregation level 16 of 4 PRBset or aggregation level 8 of 2 PRB set, each of which is an aggregationlevel lower than 24 ECCEs. When erroneous recognition of thisaggregation level occurs, there arises a problem in that a PUCCHresource is erroneously selected.

More specifically, in a case where an MTC terminal erroneouslyrecognizes reception as having received MPDCCH of aggregation level 16of 4 PRB set or MPDCCH of aggregation level 8 of 2 PRB set although thebase station has transmitted the MPDCCH using 24 ECCEs, the MTC terminaltransmits an ACK/NACK, using a PUCCH resource to be identified fromN_pucch corresponding to aggregation level 16 of 4 PRB set oraggregation level 8 of 2 PRB set.

For example, in FIG. 11 , when recognizing that the MTC terminal hasreceived MPDCCH of aggregation level 16 of 4 PRB set, the MTC terminaltransmits an ACK/NACK using a PUCCH resource (PUCCH set (0)) to beidentified using N_pucch, 0 configured for 4 PRB set, and whenrecognizing that the MTC terminal has received MPDCCH of aggregationlevel 8 of 2 PRB set, the MTC terminal transmits an ACK/NACK using aPUCCH resource (PUCCH set (1)) to be identified using N_pucch, 1configured for 2 PRB set.

More specifically, in FIG. 11 , there is a possibility that the MTCterminal cannot transmits an ACK/NACK, using the PUCCH resourcecorresponding to 24 ECCEs, which has been originally planned by the basestation. Meanwhile, there is a possibility that the base stationattempts to receive an ACK/NACK, using the originally planned PUCCHresource corresponding to 24 ECCEs, and erroneously recognizes anACK/NACK. Moreover, there is a possibility that transmission of anACK/NACK, using a not planned PUCCH resource from the MTC terminalprovides interference to a signal transmitted by another terminal.

Note that, in Option 1 (Frequency first), MPDCCH of 24 ECCEs is mappedover 4 PRB set and 2 PRB set in units of OFDM symbols, and since mappingof MPDCCH to the REs differs from MPDCCH of aggregation level 16 of 4PRB set or MPDCCH of aggregation level 8 of 2 PRB set, the problemsrelating to the above-mentioned erroneous recognition do not occur.

In the present embodiment, a PUCCH resource identifying method capableof avoiding the erroneous recognition will be described.

A base station and a terminal according to Embodiment 3 have basicconfigurations common to base station 100 and terminal 200 according toEmbodiment 1, so that a description will be given while FIGS. 6 and 7are incorporated herein.

Hereinafter, Operation Examples 4 to 6 according to the presentembodiment will be described.

Operation Example 4

In Operation Example 4, when detecting MPDCCH of 24 ECCEs, terminal 200(MTC terminal) identifies a PUCCH resource, using N_pucch, q configuredfor PRB set q to which MPDCCH of 24 ECCEs is mapped first among aplurality of PRB sets in Narrowband. For example, when MPDCCH of 24ECCEs is mapped to PRB set 0, first and then is mapped to PRB set 1,terminal 200, when detecting 24 ECCEs of MPDCCH, identifies a PUCCHresource using N_pucch, 0 configured for PRB set 0.

Accordingly, even in a case where terminal 200 erroneously recognizesthe MPDCCH transmitted from base station 100, using 24 ECCEs, as MPDCCHof the maximum aggregation level of PRB set 0, terminal 200 can transmitan ACK/NACK using the PUCCH resource secured for MPDCCH of 24 ECCEs.Therefore, it is possible for terminal 200 to avoid erroneouslyselecting a PUCCH resource when erroneous recognition 1 occurs.

Furthermore, the number of PRB pairs to which PRB set 0 in which MPDCCHis mapped first is assigned may be greater than the number of PRB pairsto which PRB set 1 in which MPDCCH is mapped later is assigned. Forexample, PRB set 0 is set to 4 PRB set, and PRB set 1 may be set to 2PRB set. In this manner, the probability of occurrence of erroneousrecognition 2 can be lowered. This is because in order for an MTCterminal to receive MPDCCH of 24 ECCEs as aggregation level 8, evenhigher reception quality than that of reception as aggregation level 16is required, so that the probability of occurrence of erroneousrecognition of 24 ECCEs as aggregation level 8 is lower than theprobability of occurrence of erroneous recognition of 24 ECCEs asaggregation level 16. Thus, when PRB set 0 is set to 4 PRB set, and PRBset 1 is set to 2 PRB set, the probability of occurrence of erroneousrecognition 2 can be lowered while erroneous selection of a PUCCHresource caused by erroneous recognition 1 is avoided, by identifying aPUCCH resource using N_pucch,0 configured for PRB set 0, when terminal200 detects MPDCCH of 24 ECCEs.

Moreover, according to the present embodiment, base station 100 andterminal 200 identify a PUCCH resource, using offset value N_pucchconfigured for a PRB set to which MPDCCH is mapped, first. Thus, as inEmbodiment 1, base station 100 and terminal 200 can identify, withoutaddition of new signaling, the PUCCH resource corresponding to MPDCCHmapped over a plurality of PRB sets as with 24 ECCEs. That is, the PUCCHresource of the case where one MPDCCH is mapped to all 6 PRB pairs inNarrowband can be efficiently identified.

Operation Example 5

In Operation Example 5, in order to avoid erroneous selection of a PUCCHresource caused by erroneous recognition 2, when detecting MPDCCH as themaximum aggregation level of a PRB set, terminal 200 (MTC terminal)identifies a PUCCH resource, using N_pucch, 0, in addition to theoperations in Operation Example 4.

For example, when detecting MPDCCH with the maximum aggregation level ofPRB set 1, terminal 200 identifies the PUCCH resource, using N_pucch,0,and when detecting MPDCCH with another aggregation level of PRB set 1,terminal 200 identifies the PUCCH resource, using N_pucch,1 configuredfor PRB set 1,

With this configuration, terminal 200 identifies a PUCCH resource, usingN_pucch, 0 for all three cases where MPDCCH is detected with 24 ECCEs,where MPDCCH is detected with the maximum aggregation level of PRB set0, and where MPDCCH is detected with the maximum aggregation level ofPRB set 1.

Therefore, even when terminal 200 erroneously detects the aggregationlevel of received MPDCCH, the PUCCH resource to be used for transmissionof an ACK/NACK signal becomes the same resource as the resource of acase where no erroneous detection occurs. Thus, erroneous selection of aPUCCH resource caused by erroneous recognition 1 and erroneousrecognition 2 can be avoided.

Note that, when base station 100 transmits MPDCCH directed to a certainMTC terminal with the maximum aggregation level of PRB set 1, and alsotransmits MPDCCH directed to another MTC terminal with ECCE #0 of PRBset 0, there arises a problem in that PUCCH resources corresponding tothe MPDCCHs collide with each other. This collision, however, can beavoided by ARO.

Moreover, in PRB set 1, only when an MTC terminal detects MPDCCH withthe maximum aggregation level, N_pucch, 0 is used, and when an MTCterminal detects MPDCCH with another aggregation level, N_pucch, 1 isused. Accordingly, with an aggregation level other than the maximumaggregation level of PRB set 1, even when base station 100 transmitsMPDCCH including ECCE #0, the probability of collision with a PUCCHresource of PRB set 0 does not change as compared with a case whereOperation Example 5 is not applied.

Operation Example 6

In Operation Example 6, in order to avoid erroneous recognition 2, whenmapping MPDCCH of 24 ECCEs, base station 100 differs the mapping orderto REs from mapping to REs with the maximum aggregation level of PRBset 1. Changing the mapping order to the REs of MPDCCH makes it possibleto avoid the occurrence of erroneous detection as the maximumaggregation level of PRB set 1 in terminal 200 (MTC terminal) whenMPDCCH of 24 ECCEs is transmitted.

Hereinafter, a specific example of an MPDCCH mapping method to REs willbe described. Note that, in the following description, MPDCCH isassigned in the order of PRB set 0 and PRB set 1 when MPDCCH is assignedto 24 ECCEs. Moreover, PRB set 0 is set to 4 PRB set and PRB set 1 isset to 2 PRB set.

Moreover, when MPDCCH is transmitted with the maximum aggregation levelof PRB set 1 (2 PRB set, herein), as in the case of EPDCCH, within PRBset 1 (2 PRB set), MPDCCH is mapped from an OFDM symbol with a low OFDMsymbol number in ascending order of frequency while vertically crossingover PRB pairs, and then moves to the next OFDM symbol and is mapped inascending order of frequency while vertically crossing over PRB pairs,likewise.

Example 1: Mirroring

In Mirroring, as illustrated in FIG. 12A, when MPDCCH of 24 ECCEs ismapped, within PRB set 1 (2 PRB set), MPDCCH is mapped from an OFDMsymbol with a low OFDM symbol number in descending order of frequencywhile vertically crossing over PRB pairs, and then moves to the nextOFDM symbol and is mapped in descending order of frequency whilevertically crossing over PRB pairs, likewise. More specifically, inMirroring, the mapping order of MPDCCH in the frequency direction oneach OFDM symbol is inverted between the case of 24 ECCEs and the caseof the maximum aggregation level of PRB set 1.

Therefore, since the mapping order of MPDCCH differs within PRB set 1between the case where MPDCCH of 24 ECCEs is mapped and the case whereMPDCCH of the maximum aggregation level of PRB set 1 is mapped, it ismade possible to avoid erroneous detection of an aggregation level in anMTC terminal.

Example 2: PRB Pair Shifting

In PRB pair shifting, when MPDCCH of 24 ECCEs is mapped, within PRB set1 (2 PRB set), MPDCCH is mapped while the PRB pair number is shifted.For example, in FIG. 12B, since 2 PRB set is assigned to PRB pair #0 andPRB pair #1, for MPDCCH of 24 ECCEs, mapping of MPDCCH of 24 ECCEs isswitched between PRB pair #0 and PRB pair #1 with respect to the case ofthe maximum aggregation level of PRB set 1.

Accordingly, since the mapping order of MPDCCH within PRB set 1 differsbetween the case where MPDCCH of 24 ECCEs is mapped and the case whereMPDCCH of the maximum aggregation level of PRB set 1 is mapped, it ismade possible to avoid erroneous detection of an aggregation level in anMTC terminal.

Example 3: OFDM Symbol Shifting

In OFDM symbol shifting, when MPDCCH of 24 ECCEs is mapped, within PRBset 1 (2 PRB set), MPDCCH is mapped while the OFDM symbol number isshifted. For example, FIG. 12C illustrates an example in which the OFDMsymbol number is shifted by three numbers. That is, within PRB set 1 (2PRB set), MPDCCH is mapped from OFDM symbol #3 in ascending order offrequency while vertically crossing over PRB pairs, and then moves tothe next OFDM symbol and is mapped in ascending order of frequency whilevertically crossing over PRB pairs, likewise. Then, when the OFDM symbolto which MPDCCH is mapped becomes the last OFDM symbol, MPDCCH moves tothe top OFDM symbol #0 and moves down to OFDM symbol #2.

Accordingly, since the mapping order of MPDCCH within PRB set 1 differsbetween the case where MPDCCH of 24 ECCEs is mapped and the case whereMPDCCH of the maximum aggregation level of PRB set 1 is mapped, it ismade possible to avoid erroneous detection of an aggregation level in anMTC terminal.

The specific example of the MPDCCH mapping method to REs has beendescribed, thus far.

As described above, according to the present embodiment, even in a casewhere terminal 200 erroneously detects the aggregation level of MPDCCH,the PUCCH resource identical to the PUCCH resource of the case where noerroneous detection has occurred can be identified, or terminal 200 canbe prevented from erroneously detecting an aggregation level of MPDCCH.Thus, it is made possible to avoid erroneous detection of an ACK/NACKsignal in base station 100. Moreover, transmission of an ACK/NACK usinga correct PUCCH resource from terminal 200 makes it possible to avoidgiving interference to a signal transmitted from another terminal.

Note that, in the operation examples described above, a description hasbeen given of a case where MPDCCH of 24 ECCEs is assigned in order ofPRB set 0 and PRB set 1, but MPDCCH of 24 ECCEs may be assigned in orderof PRB set 1 and PRB set 0.

Each embodiment of the present disclosure has been described, thus far.

Note that, in Embodiments 1 and 2, a description has been given with theexample in which 4 PRB set and 2 PRB set are assigned to non-overlappingPRB pairs in Narrowband. However, there may be a case where 4 PRB setand 2 PRB set are assigned to overlapping PRB pairs. FIGS. 13A and 13Billustrate an example in which 4 PRB set is assigned to PRB pairs #2,#3, #4, and #5, and 2 PRB set is assigned to PRB pairs #2 and #3 whichare overlapping PRB pairs. Note that, in FIGS. 13A and 13B, anassumption is made that Option 1 (Frequency first) is used for MPDCCHmapping of 24 ECCEs. More specifically, a symbol sequence of MPDCCH of24 ECCEs in Narrowband is mapped from an OFDM symbol with a low OFDMsymbol number in ascending order of frequency while vertically crossingover PRB pairs, and then moves to the next OFDM symbol and is mapped inascending order of frequency while vertically crossing over PRB pairs,likewise. Even in the case of mapping in which 4 PRB set and 2 PRB setoverlap with each other, Operation Example 2 of Embodiment 1 andOperation Example 3 of Embodiment 2 can be applied. For example, inOperation Example 2, when an MTC terminal detects MPDCCH of 24 ECCEs, aPUCCH resource may be identified using N_pucch, 0. Moreover, inOperation Example 3, when an MTC terminal detects MPDCCH of 24 ECCEs, aPUCCH resource may be identified using N_pucch configured in common to aplurality of PRB sets.

Although a description has been given with an example of a case where anaspect of the present disclosure is formed by hardware in each of theembodiments, the present disclosure can be realized by software incooperation with hardware.

Each functional block used in the description of each embodimentdescribed above can be partly or entirely realized by an LSI such as anintegrated circuit, and each process described in each embodiment may becontrolled partly or entirely by the same LSI or a combination of LSIs.The LSI may be individually formed as chips, or one chip may be formedso as to include a part or all of the functional blocks. The LSI mayinclude a data input and output coupled thereto. The LSI herein may bereferred to as an IC, a system LSI, a super LSI, or an ultra LSIdepending on a difference in the degree of integration.

Moreover, the technique of implementing an integrated circuit is notlimited to the LSI and may be realized by using a dedicated circuit, ageneral-purpose processor, or a special-purpose processor. In addition,a Field Programmable Gate Array (FPGA) that can be programmed after themanufacture of the LSI or a reconfigurable processor in which theconnections and the settings of circuit cells disposed inside the LSIcan be reconfigured may be used.

Moreover, if future integrated circuit technology replaces LSIs as aresult of the advancement of semiconductor technology or otherderivative technology, the functional blocks could be integrated usingthe future integrated circuit technology. Biotechnology can also beapplied.

A base station of the present disclosure includes: a signal assignmentsection that assigns a downlink control signal to a downlink resource,the downlink control signal including resource allocation information onPhysical Downlink Shared Channel (PDSCH); an identifying section thatidentifies a Physical Uplink Control Channel (PUCCH) resource based onthe downlink resource to which the downlink control signal has beenassigned, the PUCCH resource being a resource to which an ACK/NACKsignal for the PDSCH is assigned; and a signal separating section thatseparates the ACK/NACK signal included in the identified PUCCH resourcefrom a received signal from a terminal to which the downlink controlsignal has been transmitted, in which the downlink resource is composedof a plurality of PRB pairs, and any of a first PRB set and a second PRBset is assigned to each of the plurality of PRB pairs, and in a casewhere the downlink control signal is mapped over the first PRB set andthe second PRB set, the identifying section identifies the PUCCHresource, using an offset value configured for any of the first PRB setand the second PRB set.

In the base station of the present disclosure, mutually different offsetvalues are configured for the first PRB set and the second PRB set,respectively, and in a case where the downlink control signal is mappedover the first PRB set and the second PRB set, the identifying sectionidentifies the PUCCH resource, using an offset value configured for aPRB set assigned to a PRB pair having a minimum PRB number, among thefirst PRB set and the second PRB set.

In the base station of the present disclosure, mutually different offsetvalues are configured for the first PRB set and the second PRB set,respectively, and in a case where the downlink control signal is mappedover the first PRB set and the second PRB set, the identifying sectionidentifies the PUCCH resource, using an offset value configured for aPRB set having a smaller PRB set number among the first PRB set and thesecond PRB set.

In the base station of the present disclosure, mutually different offsetvalues are configured for the first PRB set and the second PRB set,respectively, and in a case where the downlink control signal is mappedover the first PRB set and the second PRB set, the identifying sectionidentifies the PUCCH resource, using an offset value having a smallervalue among the offset values configured for the first PRB set and thesecond PRB set.

In the base station of the present disclosure, a common offset value isconfigured for the first PRB set and the second PRB set, and theidentifying section identifies the PUCCH resource, using the commonoffset value.

In the base station of the present disclosure, mutually different offsetvalues are configured for the first PRB set and the second PRB set,respectively, and in a case where the downlink control signal is mappedover the first PRB set and the second PRB set, the identifying sectionidentifies the PUCCH resource, using an offset value configured for aPRB set in which the downlink control signal is mapped first, among thefirst PRB set and the second PRB set.

In the base station of the present disclosure, the number of PRB pairsto which the PRB set in which the downlink control signal is mappedfirst is assigned is greater than the number of PRB pairs to which a PRBset in which the downlink control signal is mapped later is assigned.

A terminal of the present disclosure includes: a receiving section thatreceives a downlink control signal including resource allocationinformation on Physical Downlink Shared Channel (PDSCH); and anidentifying section that identifies a Physical Uplink Control Channel(PUCCH) resource based on a downlink resource to which the downlinkcontrol signal has been assigned, the PUCCH resource being a resource towhich an ACK/NACK signal for the PDSCH is assigned; and a signalassignment section that assigns the ACK/NACK signal to the identifiedPUCCH resource, in which the downlink resource is composed of aplurality of PRB pairs, and any of a first PRB set and a second PRB setis assigned to each of the plurality of PRB pairs, and in a case wherethe downlink control signal is mapped over the first PRB set and thesecond PRB set, the identifying section identifies the PUCCH resource,using an offset value configured for any of the first PRB set and thesecond PRB set.

A communication method of the present disclosure includes: assigning adownlink control signal to a downlink resource, the downlink controlsignal including resource allocation information on Physical DownlinkShared Channel (PDSCH); identifying a Physical Uplink Control Channel(PUCCH) resource based on the downlink resource to which the downlinkcontrol signal has been assigned, the PUCCH resource being a resource towhich an ACK/NACK signal for the PDSCH is assigned; and separating theACK/NACK signal included in the identified PUCCH resource from areceived signal from a terminal to which the downlink control signal hasbeen transmitted, in which the downlink resource is composed of aplurality of PRB pairs, and any of a first PRB set and a second PRB setis assigned to each of the plurality of PRB pairs, and in a case wherethe downlink control signal is mapped over the first PRB set and thesecond PRB set, the PUCCH resource is identified using an offset valueconfigured for any of the first PRB set and the second PRB set.

A communication method of the present disclosure includes: receiving adownlink control signal including resource allocation information onPhysical Downlink Shared Channel (PDSCH); identifying a Physical UplinkControl Channel (PUCCH) resource based on a downlink resource to whichthe downlink control signal has been assigned, the PUCCH resource beinga resource to which an ACK/NACK signal for the PDSCH is assigned; andassigning the ACK/NACK signal to the identified PUCCH resource, in whichthe downlink resource is composed of a plurality of PRB pairs, and anyof a first PRB set and a second PRB set is assigned to each of theplurality of PRB pairs, and in a case where the downlink control signalis mapped over the first PRB set and the second PRB set, the PUCCHresource is identified using an offset value configured for any of thefirst PRB set and the second PRB set.

INDUSTRIAL APPLICABILITY

An aspect of the present disclosure is useful for mobile communicationsystems.

REFERENCE SIGNS LIST

-   -   100 Base station    -   101 Aggregation level configuration section    -   102 MPDCCH generation section    -   103, 209 Error correction coding section    -   104, 210 Modulation section    -   105, 211 Signal assignment section    -   106, 212 Transmitting section    -   107, 201 Receiving section    -   108, 208 PUCCH resource identifying section    -   109, 202 Signal separating section    -   110 PUCCH receiving section    -   111, 203 Demodulation section    -   112, 204 Error correction decoding section    -   200 Terminal    -   205 Error determination section    -   206 ACK/NACK generation section    -   207 MPDCCH receiving section

The invention claimed is:
 1. An integrated circuit comprising: receptioncircuitry which, in operation, controls receiving downlink controlinformation (DCI) mapped to one or more Physical Resource Block (PRB)sets among a plurality of PRB sets; processing circuitry which, inoperation, controls mapping an ACK/NACK signal to a Physical UplinkControl Channel (PUCCH) resource, the ACK/NACK signal being generatedbased on a detection result of data indicated by the DCI; andtransmission circuitry which, in operation, controls transmitting theACK/NACK signal, wherein the plurality of PRB sets include a first PRBset having a first plurality of ECCEs and a second PRB set having asecond plurality of ECCEs different from the first plurality of ECCEs,for the first PRB set, an index to the PUCCH resource is determinedbased on a first ECCE index in which the DCI is mapped and which isoffset by a higher layer signaling, and determined without adding a PRBvalue to the first ECCE index, and for the second PRB set, an index tothe PUCCH resource is determined based on a sum between (1) the PRBvalue and (2) a second ECCE index in which the DCI is mapped and whichis offset by the higher layer signaling.
 2. The integrated circuitaccording to claim 1, wherein the PRB value is determined based on atotal number of ECCEs in the first plurality of ECCEs included in thefirst PRB set.
 3. The integrated circuit according to claim 1, wherein,for the first PRB set or the second PRB set, the index to the PUCCHresource is determined based on a repetition level offset which iscommon for a same repetition level, the repetition level offset beingindicated by the higher layer signaling.
 4. The integrated circuitaccording to claim 1, wherein the DCI is mapped to the one or more PRBsets by prioritizing a frequency direction over a time direction.
 5. Theintegrated circuit according to claim 1, wherein, for the second PRBset, the index to the PUCCH resource is determined for distributedassignment based on: n_(PUCCH) ^((1,{tilde over (p)}) ⁰ ^()=n)_(ECCE, q)+Δ_(ARO)+n_(PUCCH,q) ^((e1)) and the PRB value, and wherein,for the second PRB set, the index to the PUCCH resource is determinedfor localized assignment based on:$n_{PUCCH}^{({1,{\overset{\sim}{p}}_{0}})} = {{\left\lfloor \frac{n_{{ECCE},q}}{N_{RB}^{{ECCE},q}} \right\rfloor \cdot N_{RB}^{{ECCE},q}} + n^{\prime} + \Delta_{ARO} + N_{{PUCCH},q}^{(\;{e\; 1})}}$and the PRB value.
 6. The integrated circuit according to claim 1,wherein, for the second PRB set, the index to the PUCCH resource isdetermined by assuming the second ECCE index is 0 when the DCI isreceived on multiple PRB sets.
 7. The integrated circuit according toclaim 1, wherein the PRB value is selected from multiple values.